Carmona, who won 19 games for the Indians in 2007, is 2-6 with a 7.42 ERA this year. He will report to the Indians' minor league complex in Goodyear, Ariz., to work on his mechanics and mental approach after he allowed 16 earned runs in his last three starts, spanning 7 1-3 innings.

The Rookie League season hasn't started yet, but Indians general manager Mark Shapiro doesn't want Carmona pitching in competitive situations right now.

"Just a demotion to the minor leagues wasn't going to ensure he'd get back on track," Shapiro said. "Through the effort to survive and adapt up here, he'd gotten into some very bad habits and routines. We need to get him not just out of the major league fray, but out of the competitive fray for a period of time. We need to assess where he is mentally, physically and fundamentally and put a plan back in place to have him realize his potential."

The 25-year-old Carmona enjoyed his best season in 2007, when he went 19-8 with a 3.06 ERA and finished fourth in Cy Young award voting. He was rewarded with a four-year, $15 million deal. He is making $2.75 million this year and is guaranteed another $11 million over the next two years. The Indians hold options through 2014.

Shapiro expects Carmona to return to the Indians at some point in 2009, but not anytime soon. He will eventually leave Goodyear and pitch again in the minor leagues when the Indians feel he is ready.

Carmona is not the first pitcher to be handed such a dramatic demotion. The Toronto Blue Jays optioned Roy Halladay to Class A in 2001, the Texas Rangers optioned Edinson Volquez to Class A in 2007 and the Detroit Tigers did it with Dontrelle Willis last year. All three have returned to the majors, with Halladay winning the Cy Young award in 2003.

"I think you look at those examples. Halladay and Volquez came to mind," Shapiro said. "We're not looking to redo his mechanics, we're going to look to solidify and reinforce his mechanics and make sure they're repeatable start to start and pitch to pitch. Those are the breakdowns that are happening."

Tomo Ohka will take Carmona's place in the rotation, but the Indians have an off day on Monday, meaning they wouldn't need a fifth starter until June 13.

Hafner had been on the disabled list since April 29 with soreness in his surgically repaired right shoulder. He is hitting .270 with four home runs and eight RBIs in 17 games.

"There will be some limitations on his workload at this point, but he feels good," Shapiro said of Hafner. "He's definitely made progress. The strength is there. It's good to have a day we're activating a player instead of placing a guy on the DL."